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Spinel‐Corundum Phase Equilibria in the Systems Mn‐Cr‐Al‐O and Co‐Cr‐Al‐O at 1373 K
Author(s) -
JACOB K.T.,
IYENGAR G.N.K.,
KIM W.K.
Publication year - 1986
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1986.tb07450.x
Subject(s) - spinel , corundum , solid solution , electron microprobe , oxide , chemistry , octahedron , spinodal decomposition , mixing (physics) , phase (matter) , analytical chemistry (journal) , crystallography , mineralogy , thermodynamics , materials science , crystal structure , metallurgy , physics , organic chemistry , chromatography , quantum mechanics
The tie lines delineating ion‐exchange equilibria between MCr 2 O 4 ‐MAl 2 O 4 spinel solid solution, where M is either Mn or Co, and Cr 2 O 3 ‐Al 2 O 3 solid solution with the corundum structure were determined at 1373 K by electron microprobe and E0AX point count analysis of the oxide phases equilibrated with metallic Co and Au‐5% Mn. The component activities in the spinel solid solutions are derived from the tie lines and the thernodynamic data for Cr 2 O 3 ‐Al 2 O 3 soiid solutions available hi the literature. The Gibbs free energies of mixing calculated from the experimental data are discussed in relation to the values derived from the cation distribution a.odel based on the site preference energies and assuming random mixing on both tetrahedral and octahedral sites. Positive deviations from ideality observed in this study suggest a miscibility gap for both series of spinel solid solutions at low temperatures in the absence of oxidation.